/Engine/Plugins/Runtime/MassEntity/Source/MassEntity/Public/MassObserverManager.h
bool OnCompositionChanged ( const [FMassEntityHandle](API\Plugins\MassEntity\FMassEntityHandle) Entity, const [FMassArchetypeCompositionDescriptor](API\Plugins\MassEntity\FMassArchetypeCompositionDescrip-) & CompositionDelta, const [EMassObservedOperation](API\Plugins\MassEntity\EMassObservedOperation) Operation )